Visible light excitation on CuPd/TiN with enhanced chemisorption for catalyzing heck reaction

Abstract

In this work, we developed plasmonic photocatalyst composed of CuPd alloy nanoparticles supported on TiN, the optimized Cu₃Pd₂/TiN catalyst shows excellent conversion (>96 %) and selectivity (>99 %) for Heck reaction at 50 °C under visible light irradiation. By in-situ spectroscopic investigations, we find that visible light excitation could achieve stable metallic Cu species on the surface of CuPd alloy nanoparticles, thereby eliminating the inevitable surface oxides of Cu based catalyst. The in-situ formed metallic Cu species under irradiation take advantage of the strong interactions of Cu with visible light, and manifest in the localized surface plasmon resonances (LSPR) photoexcitation. Visible light excitation could further promote the charge transfer between catalytic Pd component and the support TiN, resulting in electron-rich Pd sites on CuPd/TiN. Moreover, light excitation on CuPd/TiN generates strong chemisorption of iodobenzene and styrene, favoring the activation of reactants for Heck reaction. DFT calculations suggest that electron-rich CuPd sites ideally lower the activation energy barrier for the coupling reaction. This work provides valuable insights for mechanistic understanding of plasmonic photocatalysis.